The present invention relates in general to a process for the production of high purity lactones in high yield which is conducted in the liquid phase using a class of copper chromite catalysts, preferably, in the form of a slurry.
It is known to catalytically dehydrogenate monohydric alcohols to produce aldehydes or ketones. Further in the case of aliphatic diols, B. Berthon et al., Tetrahedron Letters 22 (41) 4073-6 (1961), describes the liquid phase copper oxide catalyzed dehydrogenation of four to six carbon atom diols to produce the corresponding lactones. This article also describes the production of gamma butyrolactone from butanediol.
The use of a copper chromite catalyst to convert butanediol to gamma butyrolactone is disclosed in U.S.S.R. Patent No. 193,487. This reaction is conducted in the vapor phase in the presence of hydrogen.
The dehydrogenation of aliphatic diols to form unsaturated cyclic ethers, such as 2,3-dihydrofuran from butanediol rather than such lactones, is disclosed in U.S. Pat. No. 3,817,996. This process is conducted in the liquid phase and the product is recovered in the liquid phase using a copper chromite/tungstic oxide catalyst in the presence of hydrogen.
U.S. Pat. No. 4,433,175 discloses that a catalyst comprising 35% CuO, 38% CrO.sub.3, 10% BaO, and, optionally, a silica binder can be used for the dehydrogenation of neohexanol to yield neohexanal. It should be noted that the chromium in this catalyst is hexavalent, whereas in the catalyst used in the present invention it is trivalent. The reaction is conducted in the vapor phase, and the product is recovered by separate distillation. High yield and product purity were obtained at low conversion of neohexanol.
U.S. Pat. No. 4,486,607 discloses the dehydrogenation of 3-(t-butylphenyl)-2-methylpropan-1-ol in the presence of a copper chromite catalyst suspension to yield the corresponding aldehyde. Product recovery is by distillation from the reactor.
W. Reeve et al., JACS 62,2874 (1940), discloses dehydrogenating alcohols having four or more carbon atoms per molecule to give aldehydes or ketones using a barium-activated copper chromite catalyst in the liquid phase, using ethylene as a hydrogen acceptor. Yields and conversions are low.
The preparation of ketones by the dehydrogenation of secondary alcohols in the liquid phase using a copper chromite catalyst is described by D. D. Nanvati, J. Ind. Chem. Soc 51 (5), 551-2 (1974). The products are recovered by filtration and subsequent purification by distillation. An almost quantitative yield of 2-octanone was obtained from 2-octanol.
There remains a need to provide a process for dehydrogenating aliphatic diols at high conversion to produce lactones of high purity in excellent yield. It is also desirable to provide a catalyst for such a process which will retain its catalytic activity over a long duration.